Numerical Study on Heat Transfer and Pressure Loss Characteristics of Swirl Cooling in Elliptica Tubes with Tangential Jet Inlets

The paper presents a numerical study of the heat transfer, pressure loss and flow characteristics of swirl cooling in elliptical tubes, which are compared to the counterpart of swirl cooling in a circular tube with a diameter of D=50.0 mm under equal passage Reynolds numbers and equal jet Reynolds numbers. The swirl tubes with two kinds of fixed tube length of 12D and 20D are compared, where there are sequentially arranged three tangential jet inlets over the leading tube length of 12D. The numerical results show that the swirl tubes with the tube length of 12D has a much better heat transfer performance. Under equal passage Reynolds numbers, the elliptical swirl tubes with the tube length of 12D show appreciably higher Nusselt numbers by up to 22.8% and lower pressure loss coefficients by up to 69.0% than the circular tube. Under equal jet Reynolds numbers, the elliptical tubes can reduce the global heat transfer performance modestly by up to 25.6%, but reduce the pressure loss much significantly by up to 70.6%. Mostly due to much less pressure loss, the elliptical tubes have remarkably higher thermal performance in terms of the obtained heat transfer coefficient per unit pumping power for both L1=12D and L2=20D. The numerical simulations indicate that the suppression of elliptical tubes on the swirling flow development reduces the heat transfer on the wall between the jet inlets, and decreases the wall shear force and the pressure loss in the tube.